1. Field of the Invention
The invention relates to a sheet treating apparatus in a copier, a laser beam printer or the like, and an image forming apparatus provided with the same, and more particularly to a sheet treating apparatus improved so that during the alignment and stitching process of sheets on the surfaces of which images have been formed by an image forming apparatus and which are delivered, particularly the processing operation of aligning the sheets, the grouping of the sheets by aligning means can be effected and also the alignment of the grouped sheet bundle can be effectively effected, and an image forming apparatus provided with such sheet treating apparatus.
2. Related Background Art
Generally, as sheet treating apparatuses, there have already been proposed and put into practice numerous apparatuses comprising a combination of first treating means for aligning and grouping sheets on which images have been formed and stapling a part of the bundle sheet as required, and second treating means for receiving and containing each aligned sheet bundle or stapled sheet bundle, including apparatuses disclosed, for example, in Japanese Patent Application Laid-Open No. 11-199123.
The construction of the aligning portion of a conventional sheet treating apparatus of this type is schematically shown in FIG. 33 of the accompanying drawings. In FIG. 33, the conventional sheet treating apparatus is comprised of a pair of carrying-out rollers 701 comprising a lower carrying-out roller 701a and a carrying-out roller 701b for carrying out sheets P from a sort path 700, a treating unit 800 having first treating means for receiving, aligning and grouping the sheets P carried out, and stapling a part of the sheet bundle as required, and a stack tray 900 for containing and stacking therein each sheet bundle bundle-delivered after treatment.
Knurled belts 702 are wound on several axial locations between the lower carrying-out roller 701a and the carrying-out roller 701b of the pair of carrying-out rollers 701, and sheet guides 703 are disposed at appropriate locations among the knurled belts 702.
The treating unit 800 has a treating tray 801 inclined by the downstream side (the left upper portion as viewed in FIG. 33) thereof with respect to the direction of delivery of the sheets P being positioned upwardly and the upstream side (the right lower side as viewed in FIG. 33) thereof being positioned downwardly, a trailing end stopper portion 802 at the upstream side end portion, a pair of right and left aligning members 803 in the widthwise direction of the sheet, a pair of bundle delivery rollers 804 comprising a set of lower and upper bundle delivery rollers 804a and 804b disposed downstream of the treating tray 801, a swingable guide 805 having an upper bundle delivery roller 804b on the underside of the leading end thereof, and supporting the upper bundle delivery roller 804b for movement toward and away from the lower bundle delivery roller 804a, and a pull-in paddle 806 disposed above the intermediate portion.
In this case, the lower and upper bundle delivery rollers 804a and 804b of the pair of bundle delivery rollers 804 receive the sheet P from the pair of carrying-out rollers 701 onto the treating tray 801 with the upper bundle delivery roller 804b brought into its open state in which it is spaced apart from the lower bundle delivery roller 804a by the swinging control of the swingable guide 805, and the upper bundle delivery roller 804b is brought into its closed state in which it is in contact with the lower bundle delivery roller 804a in synchronism with the termination of the reception, and also the lower bundle delivery roller 804a is rotatively driven in a clockwise direction to thereby bias the received sheet P so as to pull it back to the upstream trailing end stopper portion 802 side, i.e., the upstream side, on the treating tray 801, and then the upper bundle delivery roller 804b is again spaced apart from the lower bundle delivery roller 804a. 
Also, the sheet P biased to the upstream side is continuedly subjected to the pulling-back action by the rotative driving of the pull-in paddle 806 and also is aligned by the operation of the aligning members 803, and the feeding-in action for the end portion of the sheet by the rotation of the knurled belts 702 is applied thereto, and the sheet P is dashed against the trailing end stopper portion 802 via the sheet guides 703, and the aligning operation is terminated in this manner.
The knurled belts 702, as shown in FIG. 33, are wound on the lower delivery roller 701a adjacent to the lower portion between the pair of carrying-out rollers 701, i.e., adjacent to the treating tray 801 and are made rotatable and also, there is provided an idle runner 791 idly rotated in contact with the lower inner peripheral surface of the knurled belts 702, and during the paddling and aligning operations which will be described below, and particularly at the start of the aligning operation performed subsequently to the paddling operation, the idle runner 791 is pulled and operated toward the rearward side (the right side) as viewed in FIG. 33, and further to the supporting surface side of the trailing end stopper portion 802 by a solenoid 792 through a link 793, whereby the knurled belts are pulled toward the inner side of the sheet guide 703 above them and are deformed (as indicated by the broken line in FIG. 33) so as not to hamper the sheet P from being dashed against the trailing end stopper portion 802.
The sheet P delivered from the pair of carrying-out rollers 701 slides on the treating tray 801 until it is dashed against the dashing support surface 802a of the trailing end stopper portion 802 by its own gravity and the action of the pull-in paddle 806 which will be described later and the feeding action by the underside of the knurled belts 702 while the trailing end edge of the sheet P is downwardly guided by the sheet guides 703.
The sheet P having dashed is aligned widthwisely of the sheet by the aligning members 803 to thereby form a sheet bundle.
The sheet bundle aligned on the treating tray 801 is subjected to the stitching process and so on at the aligning position, whereafter the upper bundle delivery roller 804b is brought into contact with the lower bundle delivery roller 804a, and the lower bundle delivery roller 804a is now rotatively driven in a counter-clockwise direction, whereby the sheet bundle having been subjected to the treatment is bundle-delivered onto the stack tray 900.
In the above-described example of the conventional art, however, the knurled belts have been driven at two positions, i.e., a position in which they contact with the sheet shown in FIG. 33 and feed the end portion of the sheet to the trailing end stopper portion 802 and a retracted position in which they are completely spaced apart from the sheet and are hidden behind the sheet guides 703.
Therefore, when as shown in FIG. 32 of the accompanying drawings, the number of sheet bundles is great (the height of the bundles is great), the area of contact between the sheet P and the knurled belts 702 becomes large and therefore, the feeding-in force for the sheet P becomes greater than necessary and the sheet P might run upon the trailing end stopper portion 802 or might be buckled. On the other hand, if the height of the knurled belt 702 at the feeding-in position is made great in accordance with the case where the height of sheet bundles is great, when the number of sheet bundles stacked in the treating tray 801 is small, the area of contact between the sheet P and the knurled belt 702 will become small or they will not come into contact with each other, and the feeding-in force for the sheet will become small and it may become impossible to feed the sheet P to the trailing end stopper portion 802.
So, it is the object of the present invention to provide a sheet treating apparatus which always makes the feeding force of an endless belt member substantially constant irrespective of the number of sheets stacked on a treating tray, and can effect more stable stacking and alignment of sheets, and an image forming apparatus provided with the same.
A typical construction according to the present invention for achieving the above object comprises stacking tray means having a stacking surface for receiving and stacking sheets thereon and a stopper portion for regulating the end portions of the sheets, a delivery rotary member for delivering the sheets to the stacking tray means, an endless belt member contacting with and acting on the upper surface of the sheets on the stacking tray means, and feeding the sheet to be delivered so as to pull the end portion thereof into the stopper portion, and traction means for pulling one end of the endless belt member in a predetermined direction, and during the sheet feeding by the endless belt member, the traction means is operated in conformity with the height of the sheets stacked on the stacking tray means to thereby control the contact pressure of the endless belt member against the sheets stacked on the stacking tray means so as to become substantially constant.
The stacking tray means is inclined so that the downstream side thereof with respect to the delivery direction may become higher, and the sheet to be delivered is switched back to return with the direction thereof changed over, and the stopper portion may preferably be provided on the downstream side with respect to the direction of return of the sheet.
The endless belt member may preferably be supported with a portion of its inner peripheral surface twined around the delivery rotary member and be rotated with the delivery rotary member.
The construction may have height detecting means for detecting the height of the sheets stacked on the stacking tray means, and the traction means may be operated in conformity with the height of the sheets detected by the height detecting means.
The number of the sheets stacked on the stacking tray means may be counted to find the height of the sheets, and the traction means may be operated in conformity with the value thereof.
In the above-described construction, the endless belt member tries to feed the sheet with a substantially constant force irrespective of the stack height of the sheet bundle and therefore, the inconvenience during stacking that the sheet does not arrive at the stopper portion of the stacking tray means or is buckled or runs upon the stopper portion can be eliminated.
Accordingly, during the sheet aligning process by aligning means for effecting such treatment as a stitching process on the stacking tray means, the endless belt member can be deformed so as not to contact with the sheet by the pulling operation for the endless belt member by the traction means, whereby the smoothness of the alignment movement of the sheet in the widthwise direction thereof can be achieved, and irrespective of the stack height of the sheet bundle, the endless belt member tries to feed the sheet with a substantially constant force and therefore, the inconvenience during stacking that the sheet does not arrive the stopper portion at the rear end of the stacking tray means or is buckled or runs upon the stopper can be eliminated.
Also, the traction means is made to perform an upwardly pulling operation relative to the stacking surface of the stacking tray, whereby at a smaller movement stroke, the endless belt member can be retracted from the sheet, and the time required for control becomes short and productivity is improved, or the size of the apparatus can be made small.
Further, provision is made of height detecting means for detecting the height of the sheet bundle stacked on the stacking tray means, and the amount of traction is determined on the basis of information detected by the height detecting means, whereby it becomes possible to more accurately uniformize the amount of contact between the sheet bundle and the endless belt member and further, the feeding force of the endless belt member, and the inconvenience during stacking can be eliminated.
The present invention is constructed as previously described and therefore, the endless belt member tries to feed the sheet with a substantially constant force irrespective of the stack height of the sheet bundle and therefore, the inconvenience during stacking that the sheet does not arrive at the stopper portion at the rear end of the stacking tray means or is buckled or runs upon the stopper portion can be eliminated.
Accordingly, during the sheet aligning process by the aligning means for effecting such treatment as a stitching process on the stacking tray means, the endless belt member can be deformed so as not to contact with the sheet by the pulling operation for the endless belt member by the traction means, whereby the smoothness of the alignment movement of the sheet in the widthwise direction thereof can be achieved, and irrespective of the stack height of the sheet bundle, the endless belt member tries to feed the sheet with a substantially constant force and therefore, the inconvenience during stacking that the sheet does not arrive at the stopper portion at the rear end of the stacking tray means or is buckled or runs upon the stopper can be eliminated.
Also, the traction means is made to perform an upwardly pulling operation relative to the stacking surface of the stacking tray, whereby at a smaller movement stroke, the endless belt member can be retracted from the sheet, and the time required for control becomes short and productivity is improved or the size of the apparatus can be made small.
Further, provision is made of height detecting means for detecting the height of the sheet bundle stacked on the stacking tray means, and the amount of traction is determined on the basis of information detected by the height detecting means, whereby it becomes possible to more accurately uniformize the amount of contact between the sheet bundle and the endless belt member and further, the feeding force of the endless belt member, and the inconvenience during stacking can be eliminated.